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GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. See the documentation for help with subscribing to or submitting Circulars.

Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
Advanced Search

To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"
  1. Fermi GRB 260310A: Global MASTER-Net observations report
  2. GRB 260307B: SVOM/ECLAIRs refined analysis
  3. GRB 260208A: radio detection with the VLA
  4. GRB 260310A: Fermi GBM Final Real-time Localization
  5. GRB 260307A: Glowbug gamma-ray detection
  6. GRB 260308A: Fermi GBM Final Real-time Localization
  7. Fermi GBM Sub-Threshold Detection of GRB 260307B
  8. GRB 260307B: Mephisto optical upper limits
  9. GRB 260307B: possible NOT optical counterpart
  10. GRB 260307B: SVOM/VT upper limit with X band data analysis
  11. Fermi GRB 260307A: Global MASTER-Net observations report
  12. GRB260307B: GROWTH-India Telescope optical upper limit
  13. GRB 260307B: SVOM/VT optical candidate
  14. GRB 260307B: SVOM/C-GFT upper limit
  15. GRB 260307B: SVOM detection of a burst
  16. GRB 260307A: Fermi GBM Final Localization
  17. GRB 260211A: late-time NOT i-band observations consistent with archival flux
  18. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  19. GRB 260207A: TESS Detection and Possible VLA Counterpart
  20. EP260302a: SVOM/VT optical observation
  21. EP260306a: Gemini-North redshift z = 4.773
  22. EP260306a: SVOM/VT optical observation
  23. EP260302a: Gemini-South redshift z = 1.535
  24. EP260306a: COLIBRÍ optical observations of the fading and red counterpart
  25. EP260306a: Einstein Probe detection of an X-ray transient
  26. The EP-WXT trigger 01709258759: Las Cumbres discovery of the optical counterpart
  27. EP260302a: Optical afterglow rebrightening
  28. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  29. GRB 260303A: 1.3m DFOT optical upper limit (duplicate submission)
  30. GRB 260303A: 1.3m DFOT optical upper limit
  31. EP260214b: ATCA 6 GHz observations
  32. GRB 260211A: SVOM/VT optical rebrightening at 20 days after the burst, SN candidate
  33. GRB 260303A: SVOM/ECLAIRs refined analysis
  34. Fermi GRB 260305A: Global MASTER-Net observations report
  35. GRB 260305A: Fermi GBM Final Real-time Localization
  36. GRB 260303B: AstroSat CZTI detection
  37. GRB 260304A: AstroSat CZTI detection of a long burst
  38. SVOM/sb26030408: SVOM detection of an X-ray transient likely associated with Beta Persei
  39. GRB 260303A: SVOM/VT optical observations
  40. GRB 260303A: J-band observations with WINTER
  41. GRB 260303B: NuSTAR detection of prompt emission
  42. EP260302a: Global MASTER-Net observations report
  43. Fermi GRB 260303B: Global MASTER-Net observations report
  44. IceCube-260217A: No Candidate Transients from the Zwicky Transient Facility
  45. GRB 260228A: SVOM/ECLAIRs refined analysis
  46. GRB 260225A: SVOM/ECLAIRs refined analysis
  47. GRB 260303B: BALROG localization (Fermi Trigger 794237065 / GRB 260303559)
  48. GRB 260303B: Fermi GBM Final Real-time Localization
  49. EP260302a: analysis of the follow-up EP-FXT observation
  50. EP260227a: Gemini-South optical observations
  51. EP260302a: LCO observations
  52. EP260302a: BOOTES-7 optical counterpart detection at early times
  53. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  54. GRB 260303A: SVOM detection of a burst
  55. GRB 260228A: EP-FXT follow-up observation
  56. EP260302a: Einstein Probe detection of an X-ray transient
  57. The EP-WXT trigger 01709258736: Las Cumbres discovery of the optical counterpart
  58. GRB 251130B: TERI Gamma-ray detection
  59. GRB 260208A: TERI Gamma-ray detection
  60. GRB 260302A: Fermi GBM Final Real-time Localization
  61. EP260227a: Mondy optical observations
  62. GRB 260228A: CAHA 2.2m telescope optical upper limit
  63. GRB 260228A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  64. EP260227a: Mephisto optical detection
  65. GRID detection of GRB 260225D
  66. EP-WXT trigger 01709258652: 50cm Telescope multi-band observations
  67. EP260227a: further LCO observations
  68. EP260227a: SVOM/VT optical observation
  69. GRB 260228A: SVOM/VT optical upper limits
  70. GRB 260225D: SVOM/GRM observation
  71. EP260227A: 3.6m DOT optical afterglow detection
  72. GRB 260225B: SVOM/GRM observation
  73. GRB 260228A: SVOM detection of a burst
  74. EP260227a: FTW optical and NIR observations
  75. EP260227a: Liverpool Telescope optical observations
  76. EP260227a: LCOGT Optical Observations
  77. GRB 260226A: Asiago r-band upper limit
  78. EP260227a: Thai National Telescope observations
  79. EP260227a: likely GTC/OSIRIS+ redshift z = 2.714
  80. EP260227a: Liverpool Telescope observations
  81. EP260227a: COLIBRÍ optical observations
  82. EP260227a: NOT optical observations
  83. GRB 260225A: SVOM/VT optical continued observations and upper limit
  84. GRID detection of GRB 260223A
  85. EP260227a: Global MASTER-Net observations report
  86. EP260227a: Einstein Probe detection of an X-ray transient and refined analysis
  87. The EP-WXT trigger 01709258681 (EP260227a?): Las Cumbres follow-up observation of the optical counterpart
  88. EP/WXT trigger 01709258681 (EP260227a?): LCO candidate afterglow
  89. IceCube cascade alert 142200_1517143 retraction
  90. GRB 260226A: Insight-HXMT/HE detection of the very bright burst
  91. Konus-Wind detection of GRB 260226A
  92. GRB 260223A: 7DT detection and Medium-band SED of Afterglow
  93. EP260214a: VLT/FORS2 optical observations
  94. GRB 260225A: WINTER J-band upper limit
  95. GRB 260226A: CALET Gamma-Ray Burst Monitor detection
  96. GRB 260226A: COLIBRÍ optical upper limits
  97. GRB 260226A: LCOGT Optical Upper Limit
  98. EP-WXT trigger 01709258652: SVOM/C-GFT confirmation of a stellar flare
  99. GRB 260225D: Glowbug gamma-ray detection of a likely short burst
  100. GRB 260226A: Glowbug gamma-ray detection

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